Tumors derive from accumulative change of genes and epigenetics in normal cells, such change promotes conversion of normal cells into malignant tumors. This complex pathological change process determines diversity of mechanisms of genesis, maintenance and metastasis in different tumors. At present, surgical excision, chemotherapy and radiotherapy are common methods for clinical therapy of tumors, however surgical excision of tumors is prone to recur, and toxic and side effects of the radiotherapy and the chemotherapy are obvious.
15-20% of human cancers are associated with viral infection, for example, hepatitis B virus (HBV) and hepatitis C virus (HCV) are associated with liver cancers, and human papillomavirus (HPV) is associated with cervical cancers, etc.
Alphavirus belongs to Togaviridae, and it is a type of single stranded RNA virus with an envelope structure, transmitted mainly by a transmission media of arthropod. 13 in 29 types of alphaviruses can cause diseases of human and animals (David M. Knipe, Peter M. Howley, Chapter 23, Alphaviruses, Fields Virology 6th edition: 651-685, 2013).
Venezuelan equine encephalitis virus of alphaviruses can act as a vector to transduce dendritic cells so as to treat tumors (Moran T P, Burgents J E, Long B, et al: Alphaviral vector-transduced dendritic cells are successful therapeutic vaccines against neu-overexpressing tumors in wild-type mice. Vaccine 25: 6604-6612, 2007). However, such virus had induced fever, convulsion, abortion and even death of human, thus selectivity and safety problems severely affect use of the virus in antitumor therapy.